The present invention relates generally to an apparatus for and a method of increasing the ability of airmen flying in aircraft to resist gravity (G force) induced loss of consciousness (GLOC), and more particularly, to reducing the likelihood of gravity induced loss of consciousness resulting from when the airmen in the aircraft experiences a transition from a period of less than normal G force acceleration to greater than normal G force acceleration.
A phenomenon called the push-pull effect occurs when an airman is exposed to a period(s) of low or negative G forces followed immediately by a period(s) of positive G forces. The push-pull effect reduces an airman""s G force tolerance, and can surprise the unaware and unprotected airman with fatal results.
During flight, an airman is exposed to less than the normal baseline of 1 G force, e.g., 0 to xe2x88x921.0 G. During this exposure, blood is xe2x80x9cpushedxe2x80x9d to the airman""s head resulting in increased blood pressure in the airman""s upper body. Natural physiological responses attempt to reduce the airman""s blood pressure to normal levels by reducing the heart rate and dilating blood vessels to lower cerebral blood pressure.
If the airman is unable to compensate using natural physiological response and if the blood pressure increases too much, a condition known as xe2x80x9credoutxe2x80x9d can occur. Redout or red vision can occur at as little as two or three negative G forces causing blood vessels in the eye to rupture. Physiological investigations have reported that the parasympathetic nervous system senses the high blood pressure and automatically lowers the blood pressure by reducing the heart rate in two to four seconds and dilating blood vessels in five to seven seconds, if the low or negative G forces continue long enough. The parasympathetic nervous system returns body functions to normal after being altered by sympathetic stimulation. The sympathetic nervous system prepares the human body for violent activity in times of danger.
Upon transitioning from low or negative G forces to high G forces, the airman""s cerebral blood pressure decreases below normal as blood is xe2x80x9cpulledxe2x80x9d from the airman""s head. The sympathetic nervous system responds by increasing the heart rate in about six to eight seconds and constricting the blood vessels in about seven to fifteen seconds in an attempt to increase cerebral blood pressure.
By dramatically decreasing cerebral blood pressure and oxygen available to the brain, high G forces cause G force induced loss of consciousness or blackout. As the G forces increase, the airman experiences tunnel vision and loss of color vision. If the airman is unprepared and cerebral blood pressure is allowed to fall dramatically at high, positive G forces, the airman may lose consciousness within five to seven seconds. The brain has only five to seven seconds of latent oxygen available. If the airman is not properly protected or does not take corrective action, blackout will occur.
An airman experiences both low or negative G forces and high G forces while performing maneuvers in high performance fighter aircraft involving rapid change in direction and velocity. There exist numerous prior art approaches for dealing with high G forces and physiological effects leading to blackout in airmen. Two successful approaches for increasing the airman""s high G tolerance prevent pooling of blood in the lower extremities and force blood flow to the upper body.
The first prior art approach is a straining or tensing maneuver performed by the airman. Example anti-G straining maneuvers include the Valsalva, xe2x80x9cQxe2x80x9d, xe2x80x9cHOOKxe2x80x9d, M-1, and L-1 maneuvers. These maneuvers increase the overall hydrostatic pressure in the airman""s intravascular system and can enhance G force tolerance by approximately three Gs.
The second prior art approach is the use of a pressurized anti-G garment worn by the airman. The anti-G garment or G-suit is primarily a series of balloons within a pair of pants worn by the airman. Pressure filling the balloons squeezes the legs and abdomen of the airman reducing the amount of blood forced away from the head into the legs. An anti-G garment can enhance G force tolerance by approximately one and a half to two Gs.
An explanation of the use of the anti-G garment follows. The pressure applied to the lower anti-G garment worn by the airman to combat high G force is customarily defined by Equation 1 below, up to a maximum of eleven pounds per square inch (PSI) at nine G""s. In Equation 1, Gz represents the amount of G force experienced by the airman and P is the pressure to be applied to the anti-G garment to combat the effects of the high positive G force.
P=1.5 PSI*(Gzxe2x88x921.667)xe2x80x83xe2x80x83Equation (1)
Equation 1 is based upon empirical evidence of the human body""s physiological response to increasing G force levels from a baseline of 1.0 G. This approach does not address the effect on the airman of a transition from negative G force, where blood pressure is increased and blood is xe2x80x9cpushedxe2x80x9d to the head, to positive G force, where blood pressure is decreased and blood is xe2x80x9cpulledxe2x80x9d from the head, previously referred to as the push-pull effect.
Separately, either of these phenomena, high G force or low G force, can have a significant negative, if not deadly, impact on an airman; however, when combined in a maneuver transitioning from low G to high G, the impact of high G force on the airman is increased. Due to the physiological reactions to low G periods, the onset of blackout during a subsequent high G period occurs at a lower high G level. The human body""s tolerance for high G forces is reduced by exposure to low G force levels immediately preceding the high G forces, because of the way blood is xe2x80x9cpushedxe2x80x9d to the brain during low G periods and xe2x80x9cpulledxe2x80x9d from the brain during high G periods.
The push-pull effect is highlighted by the recent fatal crash of a Canadian CF-18 airplane. The crash occurred after the airmen experienced moderate positive G force levels following negative G force exposure. Telemetry sent throughout the flight indicated that the cause of the crash was the push-pull effect. Other aircraft incidents are suspected to be the result of the push-pull effect. This phenomenon is known and has been experienced by airmen in the aerobatic pilot community.
Additionally, the physique of an individual affects their ability to withstand G forces. Tall persons experiencing G forces are more susceptible to blackout than short persons experiencing the same G forces because the heart of the tall person has to pump blood farther to the brain than the heart of the short person. Therefore, there is a need in the art to be able to tailor the response of the anti-G garment to a specific individual""s physique.
An advantage of solving this problem is the reduction or elimination of accidents resulting from the push-pull effect, as well as providing a significant tactical advantage to protected airmen during combat maneuvers. New combat maneuvers incorporating low or negative G force levels will improve survivability of airmen and aircraft. Therefore, there is a need in the art to reduce the likelihood of loss of consciousness resulting from a transition from a period of less than normal G force to greater than normal G force. Furthermore, it would be particularly desirable to retrofit an existing aircraft with the necessary hardware and software to control an anti-G garment without requiring additional processing by aircraft computers.
Accordingly, an object of the present invention is to compensate for the push-pull effect experienced by airmen during flight maneuvers.
Another object of the present invention is to increase an airman""s tolerance during flight maneuvers to the push-pull effect.
Yet another object of the present invention is to reduce the likelihood of an airman experiencing gravity induced loss of consciousness when transitioning from low G to high G during flight maneuvers.
Another object is to avoid the use of existing aircraft computers and use an anti-G garment to compensate for the push-pull effect.
Still another object of the present invention is to tailor the response of an anti-G garment to a specific individual.
The present invention is an apparatus for and a method of reducing the push-pull effect experienced by airmen during and after a transition from a period of low or negative G force levels to high G force levels. The invention includes an anti-G controller configured to receive signals indicative of airman acceleration and anti-G garment pressure. The anti-G controller is coupled to an valve controller controlling the fill and vent valves controlling the pressure level in the anti-G garment. As the anti-G controller receives acceleration signals indicating G force levels as a function of time, the controller calculates whether the anti-G garment pressure should be increased or decreased. Increasing the anti-G garment pressure compensates for the airman""s loss of tolerance to high G levels immediately after exposure to a period of low or negative G levels.
In a method aspect of the present invention, pressure in an anti-G garment is controlled using a valve controller for increasing and decreasing the pressure in the anti-G garment coupled with a processor with memory. The memory is capable of receiving signals representing acceleration and garment pressure. The method comprises the steps of storing acceleration signals received in memory and increasing the pressure in the anti-G garment in response to a transition from a period of less than normal acceleration to greater than normal acceleration.
Still other objects and advantages of the present invention will become readily apparent to those skilled in the art from the following detailed description, wherein the preferred embodiments of the invention are shown and described, simply by way of illustration of the best mode contemplated of carrying out the invention. As will be realized, the invention is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the invention. Accordingly, the drawings and description thereof are to be regarded as illustrative in nature, and not as restrictive.